2001 Fiscal Year Final Research Report Summary
Understanding of crystal growth and reaction mechanism in hydrothermal synthesis at supercritical conditions
| Project/Area Number |
11450287
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
化学工学一般
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| Research Institution | Tohoku University |
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Principal Investigator |
ARAI Kunio Tohoku University, Graduate School of Engineering ,Professor, 大学院・工学研究科, 教授 (10005457)
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| Co-Investigator(Kenkyū-buntansha) |
SUE Kiwamu Tohoku University, Graduate School of Engineering, Assistant Professor, 大学院・工学研究科, 助手 (60333845)
WATANABE Masaru Tohoku University, Graduate School of Engineering, Assistant Professor, 大学院・工学研究科, 助手 (40312607)
ADSCHIRI Tadafumi Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (60182995)
SATO Takafumi Tohoku University, Graduate School of Engineering, Research fellow, 大学院・工学研究科, 研究機関研究員
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| Project Period (FY) |
1999 – 2001
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| Keywords | supercritical water / hydrothermal synthesis / rapid heating / metal oxide solubility / pH / formation mechanism |
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| Research Abstract |
We have conducted hydrothermal synthesis of metal oxide fine particles in supercritical water. To establish these new technologies, it is necessary to clarify characteristic and function of supercritical water as the reaction solvent. In this study, firstly, we developed the simple estimation model of equilibrium constant (dissolution and dissociation reaction) and the flow-through apparatus for measuring pH and metal oxide solubility at supercritical conditions. Secondary, we conducted the experiment of hydrothermal synthesis of several metal oxides with flow-through experimental apparatus and considered the relationship between experimental condition and generation region of nano size fine particle.
The hydrothermal reaction rate in supercritical water is higher, and the solubility of metal oxides is much lower than that in subcritical water. Both facts lead to the generation of higher super-saturation degree. The nucleation rate is expressed by the function of super-saturation degree and the surface energy according to the nucleation theory. Thus, extremely high nucleation rate can be expected at supercritical conditions. Simulation of reaction kinetics, nucleation, and crystal growth would provide quantitative explanation for the temperature dependence of the particle size. In spite of the lack of such quantitative information, the results shown in this study suggests the specific features of supercritical water hydrothermal synthesis method for the production of nanocrystals.
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